In the related art, in a case in which a multi-pin LSI package, which is used in MPU or a gate array, is mounted on a printed wiring board, a flip chip mounting method in which a semiconductor chip in which convex electrodes (bumps) made of eutectic solder, high-temperature solder, gold, or the like are formed in connection pad portions is used, and these bumps are made to face, brought into contact with, and melting/diffusion-joined to the corresponding terminal portions on a chip mounting substrate using a so-called face down method has been employed.
The semiconductor chip that is used in this mounting method is obtained by, for example, grinding a surface opposite to a circuit surface of a semiconductor wafer having bumps formed on the circuit surface and dicing the semiconductor wafer into pieces. In the process of obtaining the above-described semiconductor chip, generally, for the purpose of protecting the circuit surface and the bumps of the semiconductor wafer, a curable resin film is attached to the bump-formed surface, and this film is cured so as to form a protective film on the bump-formed surface. Typically, after being attached onto the bump-formed surface, this curable resin film has an increase in fluidity by heating, spreads between the bumps, and is close contact with the circuit surface while an upper area including a top surface of the bump and the vicinity thereof are penetrating the curable resin film. The curable resin film embeds the bump while covering the surface of the bump, particularly, the surface of a portion in the vicinity of the circuit surface. The protective film formed by curing the curable resin film in such a state protects the bump on the circuit surface being in close contact with the surface.
As a protective film forming sheet provided with the thermosetting resin film containing a thermosetting component in the above curable resin film, a protective film forming sheet formed by stacking a thermoplastic resin layer having a predetermined thermal elastic modulus on the film and further stacking a thermoplastic resin layer which is not plastic at 25° C. on the uppermost layer of the thermoplastic resin layer has been disclosed (refer to Patent Document 1). In addition, according to Patent Document 1, this protective film forming sheet is excellent in terms of the bump filling property of the protective film, the wafer workability, the electric connection reliability after resin sealing, and the like.
On the other hand, as described above, the semiconductor wafer on which the protective film is formed is divided by dicing with the protective film so as to form a semiconductor chip. Dicing is performed by cutting a semiconductor wafer at a specific position, and is generally performed by observing the semiconductor wafer from the circuit surface side using a camera in a dicing apparatus, recognizing a position of a dicing line (that is, a line indicating a place to be diced) or an alignment mark (that is, a mark for positioning a place to be diced) present on the surface of the semiconductor wafer, and specifying a cutting position of the semiconductor wafer. Therefore, in order to cut the semiconductor wafer having a protective film formed on the bump-formed surface at a correct position, the camera in the dicing apparatus needs to correctly recognize the dicing line and the alignment mark of the semiconductor wafer through the protective film, and the protective film is required to have appropriate optical characteristics. For example, it is known that yellowing is easily generated when the protective film is formed by curing the curable resin film, but when the yellowing becomes conspicuous, it is difficult to recognize the dicing line or the alignment mark, particularly by a monochrome camera.
In contrast, in the protective film disclosed in Patent Document 1, it is not certain whether or not the yellowing is suppressed.